1. Field of the Invention
This invention relates to disc cartridges such as a magnetic disc cartridge, photodisc cartridge and photo-magnetic disc cartridge. More particularly, the invention pertains to the material of the cartridge case and the shutter adapted to slidably engage therewith so as to open and close the head insertion opening in the cartridge case.
2. Discussion of the Related Art
A magnetic disc cartridge consists principally of a cartridge case in which a head insertion opening and an opening for accommodating a drive shaft are formed, a flexible magnetic disc housed rotatably in the cartridge case, a cleaning sheet secured to the inside of the cartridge case, and a shutter designed to open and close the head insertion opening in said cartridge case.
As material of the cartridge case, synthetic resins such as ABS resin, styrene resin, acrylic resin and the like have been used.
Use of a metallic shutter has the problem that as the shutter repeats its reciprocating motion, the surfaces of the cartridge case are scratched by the edges of the shutter to produce wear material, and when this wear material gets into the inside of the cartridge case and adheres to the magnetic disc surface or the magnetic head, it produces a bad effect on the recording and reproduction and become the cause of errors. For avoiding this problem, a synthetic resin-made shutter is generally used to eliminate or minimize the risk of generating wear material.
The cartridge case and the shutter which are made of synthetic resin tend to adsorb dust and contaminants in the air, and such adsorbed dust and contaminants often enter the cartridge case to become the cause of errors. It has therefore been attempted in various ways to add an antistatic agent to the cartridge case and the shutter.
Amine type organic compounds have been generally used as this type of antistatic agent, but the addition of such conventional antistatic agents to the cartridge case and the shutter would adversely affect their printability.
Usually, certain indications, such as front side and flip side, type of disc cartridge, trade marks and other commercial designs are printed on the surfaces of the cartridge case and the shutter, but when their printability is deteriorated, as mentioned above, the printing ink does not spread well and the printed indications could become blurred or disappear from the cartridge and/or shutter surfaces.